Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
  • H04N19/59—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/46—Embedding additional information in the video signal during the compression process
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
  • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards

Definitions

• Video coding and decoding method and corresponding signal
• the present invention generally relates to the field of video compression and, for instance, more specifically to the video standards of the MPEG family (MPEG-1, MPEG- 2, MPEG-4) and of the ITU-H.26X family (H.261, H.263 and extensions, H.26L).
• This invention concerns a video coding method applied to a sequence of video frames and generating a coded bitstream in which each data item is described by means of a bitstream syntax allowing any decoder to recognize and decode all the segments of the content of said bitstream.
• the invention also relates to a device for carrying out said coding method, to a transmittable video signal delivered by such a coding device, to a video decoding method for decoding said transmittable signal, and to a corresponding decoding device.
• the video is predictively encoded on a macroblock basis along different separate channels (for example luminance, chrominance, shape,).
• This prediction is performed using a motion compensation technique as described for instance in the document "MPEG video coding : a basic tutorial introduction", S.R. Ely, BBC Research and Development Report, 1996.
• a motion vector field is applied to previously decoded frames to form a prediction of the current frame to be encoded.
• a difference image called the residual signal, or simply the residual, is then obtained by subtraction of the current frame to be encoded and this prediction frame.
• This residual present along all the channels present in the input signal (luminance, chrominance, shape,...) is then binaryly encoded.
• the residual contains very few information, for instance when the energy of this residual is very low owing to the redundancy between two consecutive frames, or when the bit budget does not allow to encode much information about texture.
• the syntaxes describing the signals to be transmitted always include a description of the fact that no information is encoded and force the transmission of these descriptive elements, which are not necessary.
• mcbpc a field called "mcbpc” (see same pages 50 and 53) is used as a descriptive element for indicating which 8 x 8 chrominance blocks (U and N) have been encoded for the macroblock (when no residual signal is present, "mcbpc” takes the values "0 0").
• NLC tables are used, depending on the macroblock type, and the "00" value is therefore represented by 1 to 6 bits in the bitstream (see tables B-6 and B-7, p.339).
• GIF Common Intermediate Format
• CBP Coded Block Pattern
• the CBP element for "no residual signal” takes the decimal value "0", which is encoded on 1 bit (according to the same document, table 1, p.7), and the waste of bits is therefore 396 bits (exactly) for a CIF inter picture. It is therefore an object of the invention to propose a video coding method allowing to reduce such a waste of bits and therefore to improve the coding efficiency.
• the invention relates to a method such as defined in the introductory part of the description and which is moreover characterized in that said syntax comprises a flag indicating at a high description level, for each channel described in the coded bitstream, the presence, or not, of an encoded residual signal, and to a corresponding coding device.
• the invention also relates to a transmittable video signal consisting of a coded bitstream generated by such a video coding method and in which each data item is described by means of a bitstream syntax allowing any decoder to recognize and decode all the segments of the content of said bitstream, said video frames being, on a macroblock basis, encoded by means of a prediction technique provided for generating a prediction of the current frame and followed by a subtraction of the current frame to be encoded and this prediction frame, said subtraction leading to a difference image called residual and constituting the signal to be encoded, said signal being characterized in that it includes a syntactic element provided for indicating at a high description level, for each channel described in the coded bitstream, the presence, or not, of an encoded residual signal.
• the invention also relates to a video decoding method for decoding said transmittable video signal, and to a corresponding decoding device.
• Fig.l shows an example of an MPEG coder with motion compensated interframe prediction.
• Video_object_layer_chrom 1 bit (0 for black and white)
• Video_object_layer_additional_channels_enable 1 bit (0 for only luminance and chrominance channels)
• Video_object_additional_channels[i] 1 bit (0 for no presence)
• Examples of additional channels may be:
• Video_object_layer_lum if "Video_object_layer_lum" is 1, it means that the bitstream contains syntax elements for a luminance channel ;
• bitstream contains syntax elements for the chrominance channels, else the sequence is assumed to be black and white ; - if "Video_object_layer_additional_channels_enable” is 1, the bitstream contains syntax elements describing additional channels.
• the variable "Number_additional_channels" holds the number of additional channels.
• additional channels are present in addition to the luminance and chrominance channels, the following syntax can be found:
• Video_object_layer_shape if "Video_object_layer_shape" is 1, the bitstream contains syntax elements intented to describe a non-rectangular shape for the picture, else it is assumed to be rectangular ;
• Video_object_layer_depth if "Video_object_layer_depth" is 1, the bitstream contains syntax elements intended to describe the depth texture for the picture, else it is assumed to be a flat picture ; - other channels description can be found depending on the number of additional channels (Number_of_additional_channels).
• Vop_additional_channel_coded[i] 0 ;
• Vop-lum_channel_coded read_bit (1) ;
• Vop_chrom_channel_coded read_bit (1) ;
• Video_obj ect_layer_additional_channels_enable If ( Video_obj ect_layer_additional_channels_enable)
• Vop_additional_channel_coded[i] read_bit(l) ;
• Vop_lum_channel_coded if set to one, it indicates that some residual signal was coded for the luminance channel of the current picture, while it indicates that no luminance residual signal was coded for this picture if set to 0.
• Vop_chrom_channel_coded if set to one, it indicates that some residual signal was coded for the chrominance channel of the current picture, while it indicates that no chrominance residual signal was coded for this picture if set to 0.
• Vop_additional_channel_coded [i] if set to one, it indicates that some residual signal was til coded for the additional channel, while it indicates that no residual signal was coded for said i th additional channel if set to 0.
• the video coding method described above may be implemented in a coding device such as for instance the one illustrated in Fig.l showing an example of an MPEG coder with motion compensated interframe prediction, said coder comprising coding and prediction stages.
• the coding stage itself comprises a mode decision circuit 11 (for determining the selection of a coding mode I, P or B as defined in MPEG), a DCT circuit 12, a quantization circuit 13, a variable-length coding circuit 14, a buffer 15 and a rate control circuit 16.
• the prediction stage comprises a motion estimation circuit 21, a motion compensation circuit 22, an inverse quantization circuit 23, an inverse DCT circuit 24, an adder 25, and a subtractor 26 for sending towards the coding stage the difference between the input signal IS of the coding device and the predicted signal available at the output of the prediction stage (i.e. at the output of the motion compensation circuit 22).
• This difference, or residual is the bitstream that is coded
• the output signal CB of the buffer 15 is the coded bitstream that, according to the invention, will include the syntactic element indicating at a high description level, for each channel described in the coded bitstream, the presence, or not, of an encoded residual signal.
• Video Objects Another example of coding device may be based on the specifications of the MPEG-4 standard, hi the MPEG-4 video framework, each scene, which may consist of one or several video objects (and possibly their enhancement layers), is structured as a composition of these objects, called Video Objects (VOs) and coded using separate elementary bitstreams.
• the input video information is therefore first split into Video Objects by means of a segmentation circuit, and these VOs are sent to a basic coding structure that involves shape coding, motion coding and texture coding.
• Each VO is, in view of these coding steps, divided into macroblocks, that consist for example in four luminance blocks and two chrominance blocks for the format 4:2:0 for example, and are encoded one by one.
• the multiplexed bitstream including the coded signals resulting from said coding steps will include the syntactic element indicating at a high description level, for each channel described in the coded bitstream, the presence, or not, of an encoded residual signal.
• this syntactic element transmitted to the decoding side, is read by appropriate means in a video decoder receiving the coded bitstream that includes said element and carrying out said decoding method.
• the decoder which is able to recognize and decode all the segments of the content of the coded bitstream, reads said additional syntactic element and knows that no encoded residual signal is then present.
• Such a decoder may be of any MPEG-type, as the encoding device, and its essential elements are for instance, in series, an input buffer receiving the coded bitstream, a VLC decoder, an inverse quantizing circuit and an inverse DCT circuit. Both in the coding and decoding device, a controller may be provided for managing the steps of the coding or decoding operations.
• the coding and decoding devices described herein can be implemented in hardware, software, or a combination of hardware and software, without excluding that a single item of hardware or software can carry out several functions or that an assembly of items of hardware and software or both carry out a single function.
• the described methods and devices may be implemented by any type of computer system or other adapted apparatus.
• a typical combination of hardware and software could be a general-purpose computer system with a computer program that, when loaded and executed, controls the computer system such that it carries out the methods described herein.
• a specific use computer, containing specialized hardware for carrying out one or more of the functional tasks of the invention could be utilized.
• the present invention can also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods and functions described herein and -when loaded in a computer system- is able to carry out these methods and functions.
• Computer program, software program, program, program product, or software in the present context mean any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following : (a) conversion to another language, code or notation ; and/or (b) reproduction in a different material form.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Compression Or Coding Systems Of Tv Signals (AREA)
• Compression, Expansion, Code Conversion, And Decoders (AREA)

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• 2002
  • 2002-09-04 KR KR10-2004-7003917A patent/KR20040036948A/ko not_active Application Discontinuation
  • 2002-09-04 WO PCT/IB2002/003675 patent/WO2003026312A2/en not_active Application Discontinuation
  • 2002-09-04 JP JP2003529777A patent/JP2005503736A/ja active Pending
  • 2002-09-04 EP EP02762706A patent/EP1430726A2/en not_active Ceased
  • 2002-09-04 CN CNB028182200A patent/CN1310519C/zh not_active Expired - Fee Related
  • 2002-09-13 US US10/242,929 patent/US20030138052A1/en not_active Abandoned

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